The overall goal of this proposal is to utilize subcutaneous endometrial autotransplants in rhesus macaques as a model system for study of the factors that induce menstruation. Once established, these grafts can exhibit histological organization with regional differentiation analogous to the intact endometrium, including the presence of spiral arteries. Estrogen and progestin receptors in the grafts are present and regulated normally. The grafts menstruate in synchrony with the in situ uterus, and express matrilysin (a matrix metalloproteinase) similarly to the eutopic endometrium. Grafts can be sampled in series from the same animal during hormonally induced menses. In preliminary work with the whole macaque uterus we studied the hormonal regulation of seven endometrial matrix metalloproteinases (MMPs) around the time of menstruation. All MMPs were elevated either before or during menses, and all declined subsequent to menses, well before the onset of the luteal phase. P withdrawal led to menses and the upregulation of MMPs whether E2 was present or not, and the MMPs declined spontaneously in the absence of any added P. Consequently we hypothesize the following: P-withdrawal at the end of the menstrual cycle leads to local hypoxia due to spiral artery constriction which "injures" the endometrium and leads to increases in cytokines (and/or other mediators) that in turn lead to induction of the MMPs, which participate in the destruction of the extra cellular matrix and weakening of vascular structural integrity that are associated with menses. As menses ends and the endometrial surface heals, the cytokines and other factors would decline, and this would in turn lead to the decline in MMPs. The following specific aims are proposed to explore this hypothesis in subcutaneous endometrial autografts. 1. Examine hormonal regulation and cellular distribution of MMPs in subcutaneous endometrial autografts during induced menses. 2. Examine hormonal regulation and cellular distribution of various cytokines in subcutaneous endometrial autografts during induced menses. 3. Experimentally test the hypothesis that MMPs identified in Aim 1 or cytokines identified in Aim 2 effect menstrual breakdown by intragraft injection/infusion of MMP or cytokine inhibitors.